Just came across a card in my collection. Evil Presence. Black Boarder, Illus. Sandra Everingham

How do I know if this is from Alpha or Beta, or could it be from a different set?

Evil Presence is from the base set, so it is either Alpha or Beta if it is black-bordered. Beta cards look just like normal Magic cards. Alpha cards have more rounded corners than a regular Magic card. It will be readily apparent from just looking at the card (or lining it up with another card).

Thank you. I lined it up with another card. This must be Alpha.